1. Field of the Invention
To reduce acoustic noise during mating and unmating, an electromagnetic relay includes a nonmagnetic protrusion on the armature. This protrusion engages the core of the relay as the armature also engages the core to reduce the noise due to the collision of the armature with the core.
2. Description of the Prior Art
FIG. 1 is an exploded view of a prior art relay. FIG. 2 is a view, absent the relay cover, showing the assembled components of this prior art relay. Although reliable and effective from an electrical and mechanical perspective, the noise emitted by this relay during mating and unmating can be objectionable when used in certain applications. For example, a relay of this type, as well a comparable relays used for similar applications, can generate an audible noise, when used in proximity to a passenger compartment of an automobile. Extensive steps have been taken to reduce the noise in the passenger compartment, especially in luxury automobiles, and conventional relays used in this environment are considered to be an significant source of unwanted noise.
The prior art relay shown in FIG. 1 includes a movable contact mounted on a movable spring. The spring holds the movable contact in engagement with a normally closed contact until an increase in coil current generates a magnetic force above a pull-in threshold. The armature, which is attached to the spring then is attracted to the coil core, and the collision between the armature and the coil core results in an audible sound, which can be magnified due to resonance caused by the cover or other parts of the relay housing. Noise during drop-out occurs when the magnetic force is reduced so that the spring urges the movable contact into engagement again with the normally closed contact. This collision with the normally closed contact can also result in an objectionable noise, even thought the relay has properly performed its switching function.
FIG. 8 is a partial subassembly including an armature 40 and a spring 42 that is used in another prior art relay. A relatively soft die cut plastic or rubber pad 44 has been positioned between the armature 40 and the spring 42. Although the specific purpose of this pad 44 is not known, it may tend to reduce the audible noise which may otherwise occur during pull-in and/or drop-out. However, inclusion of this pad 44 between the armature 40 and spring 42 can significantly complicate fabrication of this subassembly.
An electromagnetic relay according to this invention includes a magnetic subassembly including a coil surrounding a core. The relay also includes an armature with a contact movable upon the application of a magnetic force when an electrical current in the coil attracts the armature into engagement with the core. A spring biases the armature so that the contact moves in an opposite direction upon separation of the armature from the core when the electrical current in the coil dissipates resulting in dissipation of the magnetic force. A nonmagnetic insert is positioned on the armature to engage the magnetic subassembly when the armature is in engagement with the core or just prior to engagement.
In such an electromagnetic relay, the nonmagnetic insert could be located on either the armature or the magnetic subassembly and in engagement with both the magnetic subassembly and the armature when the magnetic force attracts the armature into engagement with the core with the armature inclined relative to the core. An electromagnetic relay in accordance with this invention exhibits low acoustic noise characteristics upon engagement and disengagement of relay contacts, and the insert comprises means for reducing acoustic noise.